It is well recognized that wet processing in the textile industry is a major source of energy consumption. With the advent of high energy costs, and concern as to the availability of oil and natural gas, considerable effort has been expended in reducing energy usage for wet processing techniques such as bleaching, dyeing, printing and finishing.
A technology which has developed as a result of energy conservation research in the textile field is the use of foams for wet processing. By foaming techniques, the amount of liquid applied to the textiles is reduced substantially thereby greatly lowering the amount of energy required to dry the product. Not only is there a saving of energy, but foaming also permits increased productivity and a variety of other advantages.
Known foaming techniques generally utilize metering rolls and/or doctor blades for applying the correct amount of foam to the textile. A more complete discussion of such arrangements is presented in U.S. Pat. No. 4,297,860, which was granted to Joseph A. Pacifici et al on Nov. 3, 1981. This patent discloses an arrangement which includes an applicator in which foam is directed to an apertured spreader plate having on its downstream side a chamber which is trapezoidal in cross-section and filled with a bed of porous material. Foam passing through the porous bed exits from the applicator through an elongated discharge nozzle at the tapered end of the chamber.
The applicator disclosed in U.S. Pat. No. 297,868 is capable of producing a uniform foam discharge, but it suffers the disadvantage of requiring a substantial amount of purge time before this is accomplished. Furthermore, the applicator is not capable of being readily altered in orientation to permit variations in the direction of foam discharge. In U.S. Pat. No. 4,201,321, which was granted to Heinrich Patzelt et al on May 6, 1980, a device comprising a pair of concentric pipes having different diameters is disclosed as being suitable for use as an applicator in a foam generating operation. A foamable reaction mass supplied to the inner pipe passes through apertures therein into a hollow space between the pipes from which it exits through a longitudinally extending discharge slot in the outer pipe onto a conveyor where a sheet of foam is formed. In order to achieve uniform discharge of the foamable reaction mass, it is necessary that the inner pipe have a varying diameter produced by wedges introduced within the inner pipe.